1. Field of the Invention
This invention concerns a method of regenerating a motor vehicle particle filter as well as a system for controlling the regeneration of such a filter.
2. Discussion of Background
The heterogeneity of combustion processes in engines and, in particular, in diesel engines has the effect of generating carbon particles, which cannot be efficiently burned off in the engine. That is manifested by the appearance, at the outlet of the exhaust line, of the black smoke characteristic of diesel engines. This phenomenon occurs, in particular, on starting phases and on marked accelerations.
The presence of a particle filter in the exhaust line of the engine makes it possible to reduce considerably the quantity of particles, dust and other soot emitted in the atmosphere and to satisfy antipollution standards.
Controlled regenerating devices make it possible to burn off periodically the particles trapped in the filter and to avoid clogging of the latter.
This is accomplished by raising the temperature in the particle filter to a temperature of around 550 to 600° C., from which temperature the carbon particles retained in the filter spontaneously ignite.
The combustion of those particles produces a release of energy, depending on the operating conditions of the engine. That energy can be evacuated by the flow of exhaust gases coming from the engine, transmitted to the soot bed from which the filter is loaded or transmitted to the different elements comprising the particle filter or, in general, the pollution control system.
Thus, depending on the running conditions of the vehicle, it can happen that the energy released by combustion of the carbon particles might no longer be evacuated. This situation is expressed by a considerable increase in the speed of the chemical reactions generated and a runaway of the latter. That type of process can therefore give rise to a deterioration of the particle filtration system.
Devices for diagnosis of the state of operation of the filtration system generally trigger regeneration when the quantity of soot stored in the particle filter is such that regeneration can be carried out under fully controllable conditions.
Nevertheless, it is possible that under very specific running conditions, in an urban environment, for example, the conditions required for the initiation of regeneration might not be attained. The start of regeneration under those conditions can have harmful consequences on the filtering system.